The present invention relates to an ear level electronic device comprising a housing that is adapted to be worn behind the ear, in the ear, or in the ear canal, and to enclose a music synthesizer for generation of an electrical signal representing music and an output transducer for conversion of the electrical signal into sound.
Music is a sequence of sounds, such as tones, chords, etc, preferably generated in pleasant patterns. In the present context, the term music denotes a sequence of sounds that has a duration allowing a listener to listen comfortably to the music for extended periods of time. Preferably, music is a sequence of sounds with a duration that is longer than 5 seconds, preferably longer than 10 seconds, more preferred longer than 20 seconds, even more preferred longer than 30 seconds, still more preferred longer than one minute, and most preferred substantially longer than one minute.
The electronic device may relieve living beings of stress and anxiety, and in particular living beings may be relieved of stress, anxiety and upsets caused by tinnitus when listening to music synthesized by the device.
Tinnitus occurs in a subjective and an objective form. A person that has a sensation of head noises, such as buzzing, ringing, whistling, hissing, etc, is said to suffer from tinnitus. When the person has the sensation without an external cause, the tinnitus is subjective. When the head noises can be heard or measured by an examiner, the tinnitus is objective. The head noises may be heard intermittently or the noises may vary over time in another way.
It is well-known that a person suffering from tinnitus may perceive a relief from tinnitus by listening to an externally generated sound.
An externally generated sound may mask tinnitus. In general, the term masking refers to the influence on tinnitus during presence of another sound. However, the influence may continue after termination of the masking sound. The masking may be complete meaning that tinnitus is not heard during presence of the masking sound or, the masking may be partial meaning that tinnitus is heard with reduced loudness during presence of the masking sound. Masking devices generating sounds based on electronic noise signals are well-known in the art. Noise generators, e.g. pseudo-random noise generators, are employed providing stationary noise with a certain bandwidth. However, typically, random noise is not comfortable to listen to, and a positive masking effect requires that the noise is more pleasant to listen to than the tinnitus itself.
It is also known that externally generated sounds may inhibit tinnitus so that the tinnitus is not heard (complete inhibition) or is heard with reduced loudness (partial inhibition) after termination of the inhibiting sound. Typically, the tinnitus is heard again seconds or minutes after termination of the inhibiting sound but sometimes the tinnitus is inhibited for hours or days. Pure tones or noise with a narrow bandwidth have been shown to inhibit tinnitus. E.g. in U.S. Pat. No. 5,325,872, a device is disclosed for inhibiting tinnitus with pure tones by repetitively sweeping the tone across a narrow frequency interval around the frequency of the tinnitus. The repetition period may be selected between 0.1 and 1000 s.
Through habituation, a person""s perception of tinnitus may be changed by exposure of the person to sound during a longer period of time. Typically, other therapeutic methods are also included in the treatment of the person. By habituation, the tinnitus perception is changed so that nuisance caused by tinnitus is eliminated or reduced. Typically, noise signals are used for habituation. The loudness of the noise signals is adjusted so that the tinnitus is still heard. This is important for habituation to be obtained. Thus, a complete masking is not allowed.
However, it is a disadvantage of utilization of noise signals, such as white or pink noise signals, that the corresponding sounds typically cause some nuisance to the listener and may mask signals of interest to the listener.
Finally, it is known that listening to sounds in general may relieve nuisance caused by tinnitus. Listening to music may for example have a positive effect on a person""s perception of tinnitus. Further, music may also affect emotions caused by tinnitus, such as stress, by having a general relaxing effect whereby the positive effect of listening is increased. This treatment is known as desensibilisation. DE-A1-44 27 216 discloses a device generating music of a specific category selected by the tinnitus patient, e.g. classic, pop or meditation music. The music sequence may be stored magnetically on a tape or be stored in digitized form in a semiconductor memory. It is suggested that the music signals may be transmitted to a hearing aid by wireless transmission means.
Tinnitus may occur together with another hearing impairment. In WO-A-94/09606, a tinnitus masking device is disclosed for masking tinnitus where the frequency of the tinnitus occurs in a narrow frequency band in which the hearing is impaired. Thus, this device also stimulates the sensory nerves in a narrow frequency band around the frequency of the tinnitus.
It is an object of the present invention to provide an apparatus for generation of a signal representing sound that is emotionally neutral and non-distracting so that a person suffering from tinnitus may listen comfortably to sounds based on this signal for extended periods of time with a sensation of relief and thus without getting distracted with the synthesized sounds.
It is a further object of the invention to provide the apparatus in a hearing aid type of apparatus, i.e. an apparatus that is worn behind the ear, or in the ear, or in the ear canal as is well-known in the art of hearing aids.
Preferably, the apparatus is used for desensibilisation or for habituation.
The device may incorporate means for turning the music synthesizer off manually or automatically. The device may further comprise means for detecting a desired signal, such as speech, music, etc, and for turning the music synthesizer off automatically upon detection of the desired signal.
Further, the synthesized sounds should not mask any signals of interest, e.g. communication signals and other signals that the person needs or desires to hear.
According to a first aspect of the present invention an ear level electronic device is provided, comprising a housing that is adapted to be worn behind the ear, in the ear, or in the ear canal, and to enclose a music synthesizer for generation of a first electrical signal representing music and an output transducer for conversion of the first electrical signal into sound.
An ear level electronic device is a device that is worn like a hearing aid, i.e. behind the ear, in the ear, or in the ear canal, and wherein the output of the output transducer is led to the eardrum in a way that is well-known in the art of hearing aids.
The device may be incorporated into a hearing aid, such as a digital hearing aid that comprises an input transducer, the output transducer, a digital signal processing means, and the music synthesizer for generating the electronic signal representing music to be reproduced by the output transducer. Preferably, the music synthesizer is incorporated in the digital signal processing means, i.e. the digital signal processing means is adapted to perform the functions of the music synthesizer.
The music synthesizer may be adapted to generate the synthesized music at the output transducer with a loudness or amplitude level that does not mask the tinnitus completely, i.e. the user may still perceive to hear the tinnitus sound at a reduced level.
The music synthesizer may comprise a sound generator and preferably, the synthesizer comprises a set of sound generators. The sound generators may be controlled digitally.
Each sound generator may be adapted to generate an electronic signal representing a tone of a specific loudness and frequency and with a specific spectral content, thus, representing a tone with a specific sonorous figure. Further, fade-in and fade-out time constants of a generated tone may be controlled. The adjustable parameters, such as loudness, frequency, spectral content, fade-in, fade-out and tone duration, of the sound generators may be controlled digitally by a controller included in the music synthesizer.
The controller may comprise one or more pseudo-random number generators for generation of sequences of pseudo-random numbers. One or more parameters of a sound generator may be determined based on the value of a number generated by one of the one or more pseudo-random number generators. Different number generators may generate different sequences of pseudo-random numbers controlling different parameters of a selected sound generator.
In a pseudo-random number sequence, the next number can not be determined from the previous number or a short sequence of the previous numbers if the initial conditions of the number sequence are not known.
The controller may further comprise a temporal generator comprising a pseudo-random generator for determination of time periods between start of generation of successive tones.
At least one of the pseudo-random number generators may be adapted to generate a sequence of self-similar numbers, or a sequence of fractal numbers, preferably a sequence of self-similar numbers.
According to a second aspect of the present invention a tinnitus treatment method is provided, comprising the steps of synthesizing music with a music synthesizer for automatic generation of an electronic signal representing music, converting the signal into sound, and directing the sound towards an ear of a person suffering from tinnitus.
The method may further comprise the step of compensating for another hearing deficiency of the person.
The method may further comprise the step of adjusting the sound loudness to a loudness level that do not to mask the tinnitus completely.
The method may also incorporate the steps of a method of synthesizing music provided according to a third aspect of the present invention, the method comprising the steps of generating a random number with a pseudo-random number generator, and calculating parameters of a tone from the generated random number.
A sound generator may be used to generate the tone with the calculated parameters. Various parameters, such as amplitude, frequency, spectral content, fade-in, fade-out and tone duration, etc, of a generated tone may be determined based on the generated number. Different parameters may be determined from numbers occurring in different sequences of pseudo-random number sequences. Further, a period between the start of succeeding tones may be determined from a number in a sequence of pseudo-random numbers, preferably a different sequence of pseudo-random numbers. The pseudo-random number sequence may be a sequence of self-similar numbers, or a sequence of fractal numbers, preferably a sequence of self-similar numbers.
It is an important advantage of the present invention that synthesizing music with pseudo-random number generators eliminates a need for a large memory capable of storing a selection of recorded music sufficiently large for the user not to be upset with repeated listening to the same music. For example, carrying a separate device with larger capacity and thus a broader selection of music, would in general be considered cumbersome and incompatible with the daily use.
It has further been shown that music synthesized utilizing a pseudo-random number generator generating self-similar numbers, or fractal numbers, etc, is surprisingly relaxing and comfortable to listen to. Further, a music sequence generated by such a number generator is extremely long so that a person listening to the music does not perceive listening to repeated music sequences. Further it has been noted that, typically, a person with tinnitus listening to the music does not experience a complete masking of the tinnitus but rather a comfortable distraction from the tinnitus whereby the person becomes capable of concentrating on other desired matters.
Thus, by synthesizing music according to the present invention, it is achieved that the synthesized music is perceived to be virtually non-repetitive, i.e. a listener does not recognize a repeated sequence. Further, although the synthesized music substantially covers the audible spectrum, it does not mask signals of interest.
It is a further advantage that the electronic device according to the present invention may be comprised in a hearing aid or in a hearing aid type of housing to be worn behind the ear, in the ear, or in the ear canal, without a need for a remote unit for storage and transmission of music to the hearing aid or the hearing aid type of housing.
According to a fourth aspect of the present invention a binaural electronic device is provided, comprising a first electronic device of the above-mentioned type to be positioned in one ear of a user, and a second electronic device of the above-mentioned type to be positioned in the other ear of the user.
According to a fifth aspect of the present invention a method of the above-mentioned type is provided, wherein music is synthesized and directed towards one ear of a user, and different music is synthesized and directed towards the other ear of the user.
It is an important advantage of the binaural electronic device that the device is capable of synthesizing different music in different ears of a user. A user with tinnitus has experienced that listening to a binaural device according to the present invention masks the tinnitus completely even when the music is generated at a very low level of loudness. This desirable effect is believed to be caused by cognitive competition in the brain caused by listening to different music in different ears. The first and second electronic devices may produce the same music sequence displaced in time in relation to each other by an interval of at least two tones. In the present context, a person is said to listen to different music in each ear when each ear regularly does not listen to the same tones. For example, the same music sequence may be played in each ear with a specific displacement in time between the two ears. The time displacement may be adjustable by the user so that the user may perform an optimum selection of a time displacement value that provides optimum cognitive competition in the brain, i.e. reducing the perceived tinnitus effect to a minimum with a minimum of induced disturbance of the user. Alternatively, the time displacement is determined by a random difference in start-up times of each of the music synthesizers.
It is preferred that a sequence of random numbers is provided by at least one of the following methods:
selection from tabulated random numbers,
synthesized by a pseudo random number generator,
synthesized by a self-similar number generator, or
synthesized by means of natural random events, such as 1/f-noise which is well-known to have a fractal character.
Circuitry operating according to one of these methods are easily incorporated in a hearing aid, and thus a remote unit for generation and transmission of music to the hearing aid is not required.
Sometimes, a remote, portable device may be preferred, e.g. by persons suffering from tinnitus who do not have another hearing deficiency. Such a device can be of a very small size, such as the size of a completely-in-the-canal hearing aid, and may include means for wireless communication. The remote device is carried by the user and transmits music to either one or both ears, e.g. to a wireless earphone or a wireless, preferably open, earplug. A remote device may also be utilized with a binaural system for transmission of identical or different music to each ear.
In a preferred embodiment of the invention the digital signal processing means is further adapted to provide compensation for hearing impairment. This allows the hearing aid to be used by persons suffering from tinnitus and from hearing impairment.
In such an embodiment of the present invention, the synthesized music is preferably introduced in the signal path before hearing impairment compensation so that the full frequency range of the synthesized music may be heard by the user of the hearing aid.